Validation of the Intelligibility in Context Scale in Tamil (ICS-Tamil) and insights into children’s speech sound accuracy

ABSTRACT The study aimed to develop and validate the Intelligibility in Context Scale in Tamil (ICS-Tamil) among preschoolers. A total of 170 children between three-to-six years of age [125 children with typical speech and 45 children with suspected speech sound disorder (SSD)] participated in the study. Parents completed the ICS-Tamil. Children's speech production was assessed using a single-word list of 50 Tamil words. Children's responses were transcribed using the PHON software to calculate percentage of consonants correct (PCC), percentage of vowels correct (PVC) and percentage of phonemes correct (PPC). ICS-Tamil demonstrated excellent test-retest reliability (ICC = 0.99, 95% CI =  0.98-0.99) and internal consistency reliability (α = 0.92). Bivariate correlation analyses showed a moderate correlation with PCC (r s  = 0.67), PPC (r s =  0.65) and PVC (r s =  0.53), suggesting adequate construct validity. Children with typical speech scored significantly higher on the ICS-Tamil (M = 4.51, SD = 0.44) in comparison to children with suspected SSD (M = 3.46, SD = 0.54), establishing the known group validity of ICS-Tamil. A score lower than a cut-off of 4.07 on the ICS-Tamil average score demonstrated 93% sensitivity and 80% specificity in distinguishing children with suspected SSD from children with typicalspeech. Speech errors seen in children from both groups predominantly included errors in retroflex sounds. The psychometric properties of ICS-Tamil support its use to measure children's functional intelligibility across multiple environmental contexts and communication partners among Tamil-speaking children. In addition, the data on speech sound acquisition and intelligibility contribute to the much-needed data corpus to support speech-language pathologists' assessment, diagnosis and intervention planning for children with speech sound disorders in Tamil.